Researchers found that the elusive ant hunts by ambushing a larger insect and bopping it on the head, stunning the prey for several seconds. Then nestmates arrive, grab the unfortunate insect in their powerful jaws, and pull backward, spread-eagling the victim.

Unexpectedly, the team observed huge colonies of the ants in the forest canopy—up to 950,000 individuals lived in one colony spread across 200 tall trees.

In these crowded habitats, the team also discovered that the trap-jawed ants can coexist with other territorial species—an unusual behavior for ants.

"In Africa we have a situation we call no-ant land" where territorial-ant colonies have clearly defined borders, Dejean said. Should any "foreign" ant wander into the wrong area, the interloper will be attacked.

But in South America, D. armigerum and other ant species have brokered a tenuous peace—mostly on D. armigerum's terms.

Dejean observed large-scale farming of scale insects in the tree canopies, behavior common in other species of ants but seen only once before in D. armigerum. In the trees, D. armigerum and other ant species provide the scale insects with protection in exchange for the honeydew they produce from plant sap.

In the experiment, a species of carpenter ant had a scale farm in the study garden.

The carpenter ants "were attending the insects day and night. But after D. armigerum was introduced in the garden, the [carpenter ants] were obliged to leave during the day, otherwise there was a fight," Dejean said.

Mostly, though, when other ants came across D. armigerum, they'd back down rather than risk a fight.